Self-organized symmetry-breaking current filamentation and multistability in Corbino disks

A complex symmetry-breaking current instability in doped semiconductors ind uced by low-temperature impact ionization breakdown is investigated We pres ent computer simulations revealing the dynamics of the self-organized forma tion of multiple current filaments in n-GaAs Corbino disks, i.e., samples w ith concentric circular contacts. Our results explain the nascence of a fil ament in terms of two consecutive stages: a radially symmetric impact ioniz ation front spreading from the inner contact becomes unstable and breaks up into a number of streamers evolving into prefilaments. With rising current , competition between those prefilaments takes place due to the global coup ling via the road resistance. Only a small number of these survive and grow into fully developed filaments. Using the applied bias as a control parame ter we find multistability and hysteresis, with jumps in the current-voltag e characteristic caused by the spontaneous formation of additional filament s in the Corbino disk.